An architectural style is characterized by the features that make a building or other structure notable and historically identifiable. A style may include such elements as form, method of construction, building materials, and regional character. Most architecture can be classified as a chronology of styles which changes over time reflecting changing fashions, beliefs and religions, or the emergence of new ideas, technology, or materials which make new styles possible.
Styles therefore emerge from the history of a society and are documented in the subject of architectural history. At any time several styles may be fashionable, and when a style changes it usually does so gradually, as architects learn and adapt to new ideas. Styles often spread to other places, so that the style at its source continues to develop in new ways while other countries follow with their own twist. A style may also spread through colonialism, either by foreign colonies learning from their home country, or by settlers moving to a new land. After a style has gone out of fashion, there are often revivals and re-interpretations. For instance, classicism has been revived many times and found new life as neoclassicism. Each time it is revived, it is different.
Vernacular architecture works slightly differently and is listed separately. It is the native method of construction used by local people, usually using labour-intensive methods and local materials, and usually for small structures such as rural cottages. It varies from region to region even within a country, and takes little account of national styles or technology. As western society has developed, vernacular styles have mostly become outmoded by new technology and national building standards.